


His, and His Alone

by MiliusPrime



Category: FE3H, Fire Emblem, Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Jealousy, M/M, Possessive Sex, Post-Time Skip, Smut
Language: English
Status: Completed
Published: 2019-08-30
Updated: 2019-08-31
Packaged: 2020-09-30 23:50:04
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 4
Words: 4,201
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20455604
Author URL: https://archiveofourown.org/users/MiliusPrime/pseuds/MiliusPrime
Summary: Dimitri doesn’t usually fuck, but Sylvain pulled up on Byleth so he’s about to show these bitches who Byleth belongs to once and for all.





	1. His Fork

**Author's Note:**

> Dumbitri: *breaks the wall kabedon-ing byleth* "Are you carousing with other Blue Lions, a simple yes or no will suffice"  
Byleth: "no" *trying not to laugh*  
Dumbitri: *trying to be serious, is beet red tho*

Of all the things he had mourned bitterly to have lost along the course of his life, Dimtri's ability to taste food had never made anywhere near the top ten. Or top hundred. Or even top thousand.

He could smell the delicious aroma that rose from the hot meal on his plate though, and he supposed under different circumstances he _ would _ regret his inability to taste it. Right now, however, there was one thing and one thing alone that held his attention.

Sitting in front of him, Byleth was making quick work of food two times what one might deem a normal proportion, in his usual enthusiastic manner. He’d always found this equal parts amusing and, frankly, adorable, especially savoring the satisfied look on Byleth’s face when he was finished. It wasn’t often that his Professor looked so content. This however, wasn’t the sight that held Dimtri’s fierce glare.

It was, rather, a little to the left of that scene - where Sylvain was taking advantage of Byleth’s preoccupation with eating to flip his dark blue locks this way and that, carelessly touching and brushing against the pale nape of Byleth’s neck, absentmindedly passing the lone mole that adorned it, as he raucously insisted that Byleth change up his “boring hairstyle” to one undoubtedly much more flamboyant, lest he “never attract the ladies with this mop.”

With every hairstyle, the carefree knight touched Byleth more and more, and though he knew the Professor was no doubt both accustomed to Sylvain’s behavior, and didn’t care enough to stop eating… with every passing second it bothered Dimitri. Just how long was he going to touch him for?

_ Perhaps he does not want to have hands anymore. _

Dimitri stiffened and quickly banished the insidious thought that seeped into his mind - he wasn’t that person anymore. He would never again allow himself to succumb to the darkness that made him a monster.

And yet, he could not erase the increasingly intensifying desire to rip Sylvain’s hands from where they carelessly touched what was his and his alone.

It was at that moment that his Professor glanced up from his food and spoke.

“Hey Dimitri?”

“Yes?” He answered hesitantly.

“Bent your fork again.” Byleth pointed at him with his own, a teasing smirk pulling at the corner of his lips.

“Ah.” Dimtri sheepishly glanced down at the fork he had been holding - if one could even call it a fork anymore. It had been bent so severely that the metal shaft of the utensil resembled the curves around his fingers, like half of a brass knuckle. “So I have. I do hope the new kitchen staff has more patience for me in this regard than that of the Officers Academy’s kitchen staff five years ago.” 

“I’d break a fork every day too if I couldn’t taste what I ate anymore.” His professor took a comically big bite of the lasagna and sighed happily as he chewed. 

Dimitri chuckled. “Is that so? In that case, it is good that we have been able to keep you satisfied, for the sake of the silverware. You-”

“Oh oh, hold on, I just had the _ perfect _hairstyle for you occur to me, Professor - now just let me move this here and a little bit of gel and maybe trim that there… aha! Leave it to the professional!” Sylvain yet again could not seem to keep his hands to himself.

“I like my hair the way it is, though.” Byleth protested half-heartedly as he spoke around his large bite, pale fingers raised casually over his mouth.

“And _ that _ is precisely the problem, my dear Professor.”

Dimitri swallowed against the irritation that resurged again and boiled against his skin. ** _His? _ ** _ Dear? Professor _?

The legs of his chair slid backward suddenly with a loud squeaking noise as Dimtri abruptly stood, all appetite gone.

“Pardon me,” He said with a stiff bow, “I’m afraid I must return to my training now. Good day.” 

His heavy footsteps slapped against the ground angrily as he fled the scene. A training dummy would make a suitable replacement for Sylvain’s wandering hands.

\---

Despite his complete and utter destruction of several training dummies, Dimitri could not quell the anger that burned within his chest. It distracted him all throughout war meeting, and unlike usual he offered no vocal suggestions. He could tell Dedue had noticed by the concerned slant of his thickly slanted white brows before he even had a chance to draw the prince aside and ask what was wrong.

Though he of course appreciated his friend and vassal’s concern, he was a grown man and didn’t wish to get Dedue involved in his personal affairs.

“It is nothing for you to be concerned about, my friend. Just some interpersonal affairs… that I intend to handle on my own.” He’d added, recognizing the look on his vassal’s face.

“Is somebody troubling you, your Highness? You should know I am more than willing to take care of them, should you doing so put you in an unfavorable position.”

“No, no.” He had shook his head hastily. “I know you are - but it is nothing of that sort. Thank you, Dedue. 

Dedue hadn’t looked convinced, but had conceded with an, “As you wish, your Highness.”

At present, his eye kept wandering to rest on Byleth’s form. Wise, free, happy. His ally through all. The kind, warm hands he extended to everyone without hesitation. He knew his professor had an undeniable charm that drew everybody to him. It was unfair to hold that against others when he himself was the least immune, but he did anyways. When he was near him, it was so easy for him to be his best self, the hauntings of his past far behind him - he hardly ever thought of them when Byleth was close by - it felt too good. He knew he did not deserve it. He deserved to be haunted by those whose blood he’d spilled in merciless abandon, by those he’d loved that had all died while he alone lived on. He deserved to be miserable. But he didn’t want to be.

His laughter was free and full around Byleth, the shorter man’s wit and charm contagious. He wanted to feel like that all the time.

However, he supposed it was in his nature to be brutish, because he wanted to have him all to himself as well. 

His fist clenched. _ His laughter is mine. His warmth is mine. His love is mine. _

And finally, with a glance at Sylvain, lounging in his chair at the war table as if it were a cozy reunion party instead of a war strategy meeting. _ His hair is mine. _

He gripped the edge of the table hard. It did not break - which was a blessing considering the awkwardness he was sure would ensue from such an incident, as well as the fact that being responsible he’d then have to go hunt down another one - but when the war meeting was finally over there were several deep fingernail marks etched into the wood.

He didn’t care. The moment Byleth finished and dismissed the others, he rose and stalked over to stand in front of his professor, his large frame blocking the door.

“Dimitri…?”

“Professor. I need to talk to you.”


	2. His Alone

**Summary for the Chapter:**

> Alright now that you ate your pre-smut vegetals here's the first real dish.

“What’s up, Dimtri? I know this strategy seems like a long shot, but if we can pull off the diversion with the wyverns, we can take them by surprise enough to flank them and separate the main troops from the rest of the group. I know you generally prefer to fight head-on, but trust me that in this case it’s best we- mmph!”

Dimtri hadn’t meant to shove him so roughly against the wall, but his guilt over startling his beloved professor was short lived. The anger flowed hot within his veins now, and his breath came heavily as he cornered Byleth. In their intimate moments, he preferred to give the reins to Byleth, enjoying it for the fact that everything Byleth did to him was his choice - every touch, every thrust, gifts given to him freely of his own will. Now, however, he used his larger frame and superior strength to his advantage, trapping the man within his cage. 

“Why did you allow Sylvain to touch you so?” He demanded. He told himself he wanted nothing more than the truth, but to be honest he yearned desperately for a denial. “Where else have you allowed him to touch you?”

“Does his touch not bother you? Did you enjoy it?” The questions, or more accurately accusations, launched from his mouth like darts with increasing speed as his tone rose. “There is no need to cushion the truth to spare my feelings. I know Sylvain is a handsome man, sought after by many. You like being around him more than me, don’t you?”

Byleth opened his mouth to respond but Dimtri barrelled onward, suddenly afraid to hear his worst fears confirmed. Of course he liked him more, Sylvain was upbeat, cheerful, outgoing… he on the other hand was gloomy and often told he was too serious, a damper on a cheerful mood. “You have just been taking pity on me, haven’t you? I know you are only staying by my side because you are afraid I will turn into a monster at a moment’s notice. You’ve been indulging my selfish desire to monopolize you for my own well-being.”

“What?! No, of course not Dimitri, I don’t-”

“Do not lie to me!” Dimtri had meant the shout to be strong and undeniable, but to his chagrin his voice cracked pathetically on the last word. The shame in his heart mixed with the whirling jealousy and he suddenly quieted.

“...Were I a better man, I would let you go.” The very thought of doing so, of seeing his beloved Professor happy with someone else’s smile on his lips brought a fresh surge of desperate denial. “No! I cannot let you go…

… I _will_ not.” He clutched at Byleth, burying both hands his hair, pressing the length of his body into his as if by doing so, he could permanently conjoin them and make it impossible for them to be separated. _ You’re mine _. 

He was sure he held Byleth’s hair with enough strength that the shorter man could not have moved away even had he wanted to, but when he crowded his face with his own and claimed his warm pale lips with an intense, invasive kiss, he made no move to escape, simply opened his mouth compliantly with a surprised moan and let himself be ravaged. 

This frustrated him - it was not the response he wanted. He wanted him to admit to it, make his fears logical. He grasped Byleth’s waist with both hands and lifted, moving his thigh between Byleth’s legs and then set him down, grinding him forcefully up and down. Despite that it was rough, and he was being mean, Byleth still made no move to get away, instead moving his hips enthusiastically. His half-lidded eyes shone with no fear, no reluctance, only desire.

He wanted Dimtri to claim him? So be it. He would mold the shape of himself so thoroughly into his beloved that he would be satisfied with no other. With a single motion, he grasped Byleth’s pants and yanked them down to his knees, taking his underwear along with it. He spit casually into his hand and took grasp of his exposed member, slicking it all over until it was thoroughly coated before he began to pump. With his other hand he yanked back the collar of Byleth’s clothing and scraped his teeth open-mouthed against the skin. His beloved shuddered and tilted his head to expose more of the elegant column of his throat. Starting high where he was sure it would be seen, Dimitri bit and sucked, bit and sucked hard, leaving several marks. Byleth’s cock twitched in his hand every time the wet heat of his longue laved over the reddening skin.

There was no way Sylvain would touch him so casually now.

He sucked extra hard over the mole on Byleth’s neck that Sylvain had touched. Now satisfied with his work up top, it was time to make his claim elsewhere. He knelt, continuing to tug on Byleth’s cock as he raked his teeth over the insides of his thigh. This time when he bit and sucked, breathless moans of “oh shit,” “ughhh”, “feelssogooood”, and “_ Dimitri _” graced his ears with every new mark. Precum leaked from the tip of Byleth’s cock’s swollen head, and he couldn’t resist halting his movements to rub his thumb roughly pressing into the tip and circling around it for several moments before returning to jerking him off. After Byleth’s thighs had been thoroughly marked with undeniable evidence of Dimitri’s tongue and teeth, he straightened back up and resumed his attack on Byleth’s lips, greedily swallowing all of the pleasured groans for himself. 

He kissed him hard and messy, til Byleth’s lips were red and swollen and saliva glistened around his mouth - good. Evidence of their mingled passion, plain to see. 

“Shit, Dimitri - ah!” I’m gonna…come…!” Byleth breathed shallowly, hips bucking rhythmlessly into Dimitri’s hand now as the beginning of ecstasy shone in his deep blue eyes. Dimitri kissed him again as Byleth went over the edge, as if to capture all the spasms of pleasure through their connection. His beloved’s pleasure was _ his _ only to have, his only to witness. 

When Byleth slumped against the wall, finished, he took the opportunity to lower himself to Byleth’s stomach, licking up the come that had splattered against the hard muscles of his abdomen. This was his too - and there was no taste to make doing so an obstacle, though he almost wished he could, just so that he could claim to be the only one to know that too.

He wasn’t done yet though. He wanted Byleth to be ruined for all others. He wanted his imprint on his heart and his body to be permanent. So that _ he _ would be the one his beloved clung to, forever more.

Dimitri rose and wrapped his arms around his wrecked professor, and carried him to the table. Setting him against it was the only gentle motion he’d done so far, and he insistently pushed Byleth’s torso forward until he was bent over the table completely, baring his pale ass and the swell of his balls to Dimtri’s view.

**Notes for the Chapter:**

> Dimtri is a nasty boar and well, he can't taste the yucky cummies so why wouldn't he take that for himself too? Ha ha  
Anyways press f to pay respeccs to Byleth's ass next chapter :pray:


	3. His, Only

**Summary for the Chapter:**

> Y'all heard of carbon imprint? Now get ready for dick imprint.

Despite his show of dominance, Dimitri still felt strangely vulnerable enough that he only loosed his own member from within the confines of his pants, and bared nothing more. He wanted to press in immediately, but having been the one usually on the receiving end, he knew that would only bring pain to his beloved, not pleasure. Despite the excitement that lit up his blood like fire during these intimate moments, he was not so aroused to have lost _ all _ common sense. 

His fingers probed Byleth’s lips, rubbing against them gently until they parted pliantly under the pressure, and he slipped his fingers into Byleth’s mouth. They had scarcely touched his tongue before Byleth licked and swirled and sucked. Dimitri’s stomach tightened - of course Byleth was still in control, always, even when letting him take the lead - and did all he could to resist the desire to put something else between his fair lips to suck. He withdrew his fingers from Byleth’s mouth - they made a lewd pop as his cheeky beloved sucked hard on them to resist the withdrawal - and sufficiently wet as they now were, pressed them against the tight ring of muscles around Byleth’s hole.

While he circled and prodded and massaged with the fingers of one hand, his other grasped his own stiff member and slid it against Byleth’s - erect again, so soon after coming, which spoke volumes to his professor’s incredible stamina - shifting his hold to encompass them both as he rubbed them together.

Shivers of pleasure shot down his spine with every pass of their shafts through his hand - for once he was glad to have freakishly large hands - and though he was unsure who’s precum was now slicking the movement making it feel _ incredible _, he forced himself to focus on his other hand’s job, getting the tight muscles of Byleth’s anus to relax. 

He didn’t intend to be gentle once Byleth was prepared, so he took his time.

After several minutes of circling, probing, and spreading he was ready. And so was his beloved, from the elegy of impatient groans and grunts that slipped from his lips. Slipping his member in between the pale cheeks of his lover, he rubbed up and down, making a slippery pre-cum mess of Byleth’s ass. 

“If you don’t… put it in, _ now _, I’m... finding someone else who will.” Byleth bit out threateningly, clearly at his patience’s end with all the teasing. Although Dimtri knew he was being facetious, the very thought of someone else doing so had Dimitri firmly pressing his cock all the way into Byleth’s ass til he was in to the hilt, and Byleth got what he wanted after all. 

The tight walls of Byleth’s ass squeezed around his member and Dimitri had to inhale slowly and deeply through his nose - it felt so good it hurt, and he intended to last long enough to fuck his shape into his beloved’s body. When he felt ready to move again, he grasped Byleth’s pale hips and thrust in sharply and ground in a circle. Byleth’s gasp and satisfied sigh had him repeating the motion, thrusting as deeply as possible and holding before drawing out, watching as the ring of Byleth’s anus clung to his member as if unwilling to let him pull out. It was not self-cognizant of course, but to Dimitri it was an extremely gratifying notion. 

He would have kept repeating the motion just to see the sight again, but he felt a tightening building in his core that reminded him his time was limited. 

Dimitri kneed Byleth’s legs further apart and securely gripped his waist before lining him up with his member and thrust in roughly, back and forth without pause, setting a punishing pace. 

In minutes Byleth was throwing his head back in pleasure and insisting he not stop - though Dimitri’s breath came in gasps and sweat already beaded on his forehead, it was from pleasure, not exertion, and Byleth needn't have pleaded for such since Dimitri had no intention to let up on pounding the shape of his cock into his ass any time soon.

His sweaty palms slid against Byleth’s sides and he readjusted his grip, the only pause in his assault.

Dimitri would have worried about the rapidly expanding pressure in his abdomen signaling the end of his ability to last, but readjusting his grip had the unexpected effect of angling his hard member to rub roughly against Byleth’s prostate with every stroke, which had his beloved gasping and moaning more vocally than he’d ever heard the shorter man be. 

“So… rough! Gonna… come, ungh... _ shit _!” Byleth bit out a cry of ecstasy that would have concerned Dimitri to be one of pain could he not feel the shift of Byleth’s balls as he came and the small clenching tremors of his anus as the muscles twitched in orgasm.

Though tempted to finish with him like usual, Dimitri wasn’t yet satisfied, and though he slowed his thrusts for a moment to allow his beloved to recover, once he could no longer hear labored breath, he resumed his rough tempo, this time reaching down to stroke Byleth’s member at the same time.

He would drown his beloved in a wild ocean of sensation until the sole thing he could think of was _ him, only _. 

**Notes for the Chapter:**

> Dimitri's freakish strength is canon and he's having fun with it. Byleth is having fun with it too, for now, but he's gonna have less fun with it tomorrow when he can't sit down.  
Don't try this in real life kids, fantasy characters don't need to use lube, you do.


	4. His Mess

**Summary for the Chapter:**

> Ya nasties.

Dimitri’s balls were so tight from resisting the urge to come that they almost felt like they were on fire - in a bad way. The head of his cock was so swollen it was past red and onto purple, but as sweat rolled down Dimitri’s now thoroughly red face - exhaustion _ and _ pleasure this time, he gritted his teeth, determined to eke a fourth orgasm out of his beloved.

They had made an utter mess of the war table, a slurry of mixed precome, come, and sweat splattered across the dark wood - Dimitri got a feeling it would be his task to clean it. That was probably for the best though, because he could already see how red Byleth’s anus was as he struggled to keep up the now much less punishing force of his thrusts. In his experience, half the force he had used would have been enough to keep _ him _ squirming in his seat for at least two days afterward, so he could very well not expect anything more of his professor.

Byleth’s groans were quiet now, low and more taken from his throat than given, as if he could hardly bear to feel more pleasure. Yet, he still had the energy to slot his hips back against Dimitri’s, preventing them from separating.

They had been united, him deep in Byleth’s heat, for what he assumed was the better part of an hour - though he wasn’t keeping track - and he relented that after this one he would finish, having thoroughly marked his claim.

Dimitri stroked near the base of Byleth’s cock, careful to avoid the over-sensitive head now, knowing how painful a touch there could be after having come several times. The entire shaft was coated in slick and though his wrist was tired, his hand slid easily up and down.

Byleth seemed eager to finish and be done, the pace with which he threw his hips back to swallow Dimitri’s long, hard member out-pacing Dimitri’s own strokes. Were he not at the very fringes of control, he would have stilled his professor's hips to remain in control. Instead, in his exhaustion, he accepted that despite his efforts Byleth somehow always remained in control of the situation.

“Come one last - time for me, beloved.” He tried to sound forceful as he punctuated the words with a thrust, but his breathlessness took away from any authoritativeness that would’ve been present in his tone. He shifted his other hand to stroke and press against Byleth’s perineum, stimulating his prostate now from both sides. He grew desperate, feeling his own end swiftly approaching, and groaned as he pressed harder.

No sooner had he registered the shuddering spasm of muscles that indicated Byleth’s release than he was having his own, closing his one good eye as white hot pleasure exploded out from where he’d kept it tightly bound in his abdomen this whole time. He grasped the edge of the table, his legs briefly going numb from the intensity. He’d been edged before, but had never denied himself release this long, never let the pleasure build to this extent. 

It took him several minutes to recover, hissing as he withdrew his softening member from Byleth’s now thoroughly fucked-red ass, the friction of his walls against his sensitive head painful.

Byleth just slumped against the table, and made a sound that was half-wheeze, half-laugh. The sound shook his body and a small dribble of come escaped his now somewhat gaped hole. There was a different kind of fierce pleasure, this time in Dimitri’s heart, at the sight of their union.

“So.” Byleth laughed breathlessly. “You either… _ really _ don’t like the plan or… you’re jealous I let Sylvain… be my personal stylist earlier.” He said between heavy breaths, tone warm and amused.

Dimitri wanted to deny his jealousy, but he had no other explanation for the marks that peppered Byleth’s pale skin like odd large mosquito bites, nor how he had attempted a new role in their intimacy. Chagrin warmed his cheeks.

“... I prefer your current hairstyle.” He said defensively. “I have never understood the need for high-maintenance styles when one frequents the battle field.” His own shaggy long blond hair was a testament to that.

Byleth pushed himself up from the table with a grunt, his muscles popping as he stretched from being in such a bent over position for so long. He pulled up his pants with a slight grimace at the wetness - Dimitri took the opportunity to tuck himself away as well. With a rueful glance at the closed but unlocked door, and then the rather messy table, Byleth strode over to envelop Dimitri in a hug.

“You don’t need to worry about Sylvain, or anyone else, Dimitri. I’m yours.” Byleth mumbled against his chest. A rare moment of candidacy, then he pushed back from the hug before Dimitri could place his arms around him likewise. “And so is this mess!” He chirped with a laugh, pointing to the table.

He bounded toward the door. “I’m off to go take a bath and change clothes. Guess I should get used to the idea of standing for war meeting the next two days.” He said with a wince, and then slipped out the door after flashing Dimitri a saccharine mischievous smile.

Dimitri shook his head and smiled despite himself. Though left behind, Dimitri’s fears were long gone. He knew without a doubt that Byleth was his, and his alone.

**Notes for the Chapter:**

> Byleth says thanks for all the Fs, they're gonna get him through the next two days of being unable to sit down. c:  
Dumbitri is a sappy dork.
> 
> For those who might ask, this isn't canon m!byleth this is my own m!byleth from my fic Two Souls (you may have noticed the different personality. Or rather the presence of A personality period instead of nodbotting.


End file.
